The fine structure of the mature Bruch's membrane is well established; however, its normal morphological development has received little attention in the currently available literature. Moreover, the ultrastructural histochemistry of Bruch's membrane is an unexplored field of investigation. The purpose of this proposed research program will be to examine in detail the fine structural development of the fibrous connective tissues within Bruch's membrane of the vertebrate eye. Obsevations will be obtained by means of transmission electron microscopy. The domestic fowl will be used as a source of embryonic tissue. The normal development of the various fibrous connective tissues will be observed first. Subsequently, experimental embryos will be exposed to enzymes known to specifically digest certain of the fibrous connective tissues. Exposure to enzymes will occur both before and after fixation in different specimens. Other tissues will be exposed to ruthenium red. All tissues will be fixed in buffered aldehydes, dehydrated and otherwise prepared for conventional electron microscopy. A metallic porphyrin stain will be used to specifically identify elastin. This investigation will ultimately characterize the developmental morphology and the yet unknown histochemistry of the fibrous connective tissues within Bruch's membrane at the level of fine structure.